The Supreme Court on Monday waded into a complicated dispute over a law aimed at keeping immigrant families together in a case that underscores the occasionally tense relationship between immigration proponents and the Obama administration as Congress debates immigration reform.

The justices said Monday they will hear an appeal from the Obama administration arguing that children who have become adults during their parents' years-long wait to become legal permanent residents of the United States should go to the back of the line in their own wait for visas. Under U.S. immigration law, children 21 and older cannot immigrate under their parents' applications for green cards, even if the parents' application took decades to process.

An immigration spokesman declined to comment on the case Monday. The Obama administration has argued in the past that the thousands of green card applicants who lost their place in line for U.S. residency when they turned 21 do not merit priority status when they file their own visa applications.

Immigration advocates said it is hypocritical of the Obama administration to tell Congress that the nation's immigration laws are too tough and need to be rewritten, while at the same time insisting on conservative interpretations of those laws when processing family visa applications. President Barack Obama has vowed to help immigrants obtain legal status while also deporting record numbers of immigrants.